Diesel engines are provided with exhaust purification devices with the object of reducing particles and harmful gases which occur in diesel engine exhaust gases. To regulate emissions from vehicles there are various standards and legal requirements, which govern permissible levels for exhaust discharges. Vehicles are consequently provided with various kinds of purification devices for exhaust gases in an exhaust gas system in order to meet legal requirements. The exhaust gas system may be arranged for example in a silencer fluidly connected to an exhaust pipe system of a vehicle.
Silencers are used in internal combustion engines to damp engine noise and reduce emissions and are situated in the engine's exhaust system. Internal combustion engines provided with a silencer may be used in various different applications, e.g. in heavy vehicles such as trucks or buses. The vehicle may alternatively be a passenger car. Motorboats, ferries or ships, industrial engines and/or engine-powered industrial robots, power plants, e.g. an electric power plant provided with a diesel generator, locomotives or other applications may have combustion engines with silencers. The silencer comprises a diesel particulate filter (DPF), also called particulate filter in this context, for exhaust gas after treatment. The particulate filter is intended to catch particles, such as soot particles oxidized into ash. Usually, such a silencer is mounted primarily with regard to available space in the vehicle and without taking into account that the silencer should be dismantled easily, or be easily accessible when serviced. The particulate filter in the silencer may need to be dismantled in order to be replaced or cleaned of deposited ash, and, in connection therewith, the silencer also usually needs to be dismantled at least partly. This dismantling may become considerably difficult since the silencer may weigh between 100 to 150 kg and is not always easily accessible. The particulate filter itself needs to be replaced or cleaned at certain intervals since accumulated ash increases the back pressure in the exhaust system, which entails increased fuel consumption, for instance. In addition, the accumulated ash may render it difficult for the exhaust gases to get in contact with a catalytic coating in the oxidation catalyst, whereby oxidation of the soot particles into ash is obstructed. Therefore, the ash needs to be removed from the particulate filter.
Usually, the cleaning and/or replacement of the particulate filter takes place in connection with service, which typically entails dismantling of the silencer and the particulate filter with approximately one year's interval. In cases with high mileages, typically above 300 000-400 000 km, for a cargo vehicle with a diesel engine driven with alternative fuels, cleaning of the particulate filter may need to be carried out at even shorter intervals. The accumulated ash can be difficult to remove and different environmentally unfriendly solvents may be needed to remove the ash. Also the removal of ash may be laborious and time consuming. It is thus desirable that cleaning of the particulate filter is facilitated.
There have been several attempts in the prior art to facilitate cleaning of a particulate filter. For example, EP2767690A1 discloses a device for use in cleaning of a particulate filter comprising a disc unit having apertures and designed to let through air when cleaned through a suction device connected to the silencer sucking air through the opening and backwards through the particulate filter. However, it is desirable to avoid further components in the silencer that may increase the weight of the silencer.
WO2014038724 discloses a purification system in which a liquid is supplied to a particulate filter to promote movement of ash to rear parts of the particulate filter. The particulate matter, which is moved in this way, is then removed by a subsequent removal processing step. Thus, the particulate matter still needs to be removed from the particulate filter in a particular process step. The document WO 2008/053462 A1 describes an example of how cleaning a particulate filter in a silencer may occur without the filter having to be dismantled from the silencer. However, the particulate matter still needs to be removed from the particulate filter in a separate process. Further, DE4313132A1 discloses a cleaning method in which diesel particulate filter for an exhaust system of a diesel engine is cleaned of deposited particles by means of a rinsing liquid, which may be water. However, the cleaning method is performed in a separate process step in which water is lead to the particulate filter via a specific liquid inlet and whereby an interruption in the operation of the diesel engine is required.
Even though there are prior art solutions on how to remove particulate matter from particulate filters, there is still a need to improve removal procedures in the existing exhaust gas systems. There is also a great need for a high degree of exhaust gas purification in combustion engines.